1. Field of the Invention
The present invention generally relates to a drag roller device adapted for printing apparatuses, and, more particularly relates to a drag roller device equipped with various cleaning mechanisms for cleaning the circumferential surface of the drag roller.
2. Description of the Prior Art
Conventionally, printing apparatuses have employed various drag roller devices to the conveyance of a printed material, for example as shown in "Newspaper Printing; Printing Edition Revised Version" published by Nippon Shinbun Kyokai (Japan Newspaper Association) on Oct. 31, 1980, line 21 to 34 in the left column on page 61, and Japanese Patent for Utility Model Publication No. 1-30449 entitled "Rotary Press Printing Apparatus". In these conventional documents, a typical drag roller device includes a plurality of drag rollers arranged at the downstream side of a printing section. A continuous sheet such as a paper web commonly used as a material to be printed is conveyed among the plurality of drag rollers. The continuous sheet is partially wound around the circumferential surface of the drag roller, or an additional roller forcibly brings the continuous sheet into contact with the circumferential surface of the drag roller to apply the traveling motion to the continuous sheet. Further, the plural drag rollers are driven in such a manner that the circumferential speed of the drag roller is slightly faster than the upstream drag roller so as to feed the continuous sheet to the downstream side with always applying tension thereto.
In a printing process for newspapers, both surfaces of the continuous sheet are printed at the same printing section and fed by the above described drag roller device. The circumferential surface of the drag roller is easily stained by the printed ink on one surface of the continuous sheet which is in contact with the drag roller. Particularly, in the drag roller device including the additional roller which forcibly brings the continuous sheet into the circumferential surface of the drag roller, the circumferential surface of the drag roller is remarkably stained because the printed surface is strongly pressed on the circumferential surface of the drag roller. Further the stained surface of the drag roller will also stain succeeding printed surfaces of the continuous sheet.
The additional roller for bringing the continuous sheet into contact with the drag roller is also stained by the printed surface of the continuous sheet.